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    <title>ShellCheck: SC2307 – 'expr' expects 3+ arguments but sees 1. Make sure each operator/operand is a separate argument, and escape <>&|.</title>
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    <h1>SC2307 – ShellCheck Wiki</h1>
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    <h2
id="expr-expects-3-arguments-but-sees-1-make-sure-each-operatoroperand-is-a-separate-argument-and-escape-">'expr'
expects 3+ arguments but sees 1. Make sure each operator/operand is a
separate argument, and escape &lt;&gt;&amp;|.</h2>
<h3 id="problematic-code">Problematic code:</h3>
<div class="sourceCode" id="cb1"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb1-1"><a href="SC2307.html#cb1-1" aria-hidden="true" tabindex="-1"></a><span class="co"># | not escaped</span></span>
<span id="cb1-2"><a href="SC2307.html#cb1-2" aria-hidden="true" tabindex="-1"></a><span class="fu">expr</span> 1 <span class="kw">|</span> <span class="ex">2</span></span>
<span id="cb1-3"><a href="SC2307.html#cb1-3" aria-hidden="true" tabindex="-1"></a><span class="co"># &gt; not escaped</span></span>
<span id="cb1-4"><a href="SC2307.html#cb1-4" aria-hidden="true" tabindex="-1"></a><span class="fu">expr</span> <span class="st">&quot;</span><span class="va">$foo</span><span class="st">&quot;</span> <span class="op">&gt;</span>= <span class="st">&quot;</span><span class="va">$bar</span><span class="st">&quot;</span></span>
<span id="cb1-5"><a href="SC2307.html#cb1-5" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb1-6"><a href="SC2307.html#cb1-6" aria-hidden="true" tabindex="-1"></a><span class="co"># Missing spaces around +</span></span>
<span id="cb1-7"><a href="SC2307.html#cb1-7" aria-hidden="true" tabindex="-1"></a><span class="fu">expr</span> 1+2</span>
<span id="cb1-8"><a href="SC2307.html#cb1-8" aria-hidden="true" tabindex="-1"></a><span class="co"># Unexpected quoting around an expression</span></span>
<span id="cb1-9"><a href="SC2307.html#cb1-9" aria-hidden="true" tabindex="-1"></a><span class="fu">expr</span> <span class="st">&quot;1 + 2&quot;</span></span></code></pre></div>
<h3 id="correct-code">Correct code:</h3>
<div class="sourceCode" id="cb2"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb2-1"><a href="SC2307.html#cb2-1" aria-hidden="true" tabindex="-1"></a><span class="fu">expr</span> 16 <span class="dt">\|</span> 7</span>
<span id="cb2-2"><a href="SC2307.html#cb2-2" aria-hidden="true" tabindex="-1"></a><span class="fu">expr</span> <span class="st">&quot;</span><span class="va">$foo</span><span class="st">&quot;</span> <span class="dt">\&gt;</span>= <span class="st">&quot;</span><span class="va">$bar</span><span class="st">&quot;</span></span>
<span id="cb2-3"><a href="SC2307.html#cb2-3" aria-hidden="true" tabindex="-1"></a><span class="fu">expr</span> 1 + 2</span></code></pre></div>
<h3 id="rationale">Rationale:</h3>
<p>ShellCheck found an <code>expr</code> command with 1 or 2 arguments.
<code>expr</code> normally expects 3 or more.</p>
<p>Generally, this happens for one of two reasons:</p>
<ul>
<li>You are using an operator like <code>|</code>, <code>&amp;</code>,
<code>&gt;</code>, <code>&gt;=</code>, <code>&lt;</code>,
<code>&lt;=</code>, which needs to be escaped to avoid the shell
interpreting it as a pipe, backgrounded command, or redirection.</li>
<li>You don't have spaces around operators and operands (or have bad
quotes) which causes them not to be separate arguments.</li>
</ul>
<p>Make sure each operator or operand to <code>expr</code> is a separate
argument, and that anything containing shell metacharacters is escaped.
The correct code shows examples of each.</p>
<h3 id="exceptions">Exceptions:</h3>
<p>None</p>
<h3 id="related-resources">Related resources:</h3>
<ul>
<li>Help by adding links to BashFAQ, StackOverflow, man pages, POSIX,
etc!</li>
</ul>
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